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[mrmopar22]

I'm new to this site and really like what I see, thank you.

I put in a wood boiler in November and is my first experience with a boiler type set up.  Without any past knowledge it has truly been a trial by fire learning.  I'll set the stage for my story in hopes that some detail might trigger a clue for the experienced boiler operator.
It's a portage and main ML30 with 120 gallon capacity.  The pump is a B&G 100 mounted on the back side of the stove with a 1"X 12" down pipe into the inlet.  The stove sets lower than the house so the pump has to pump it up hill - probably a 10' or 12' difference.  The underground pex is 1" and runs 170' from the stove into the house through the water heat exchanger, then the air heat exchanger, and returns through the garage heat exchanger and then back to the stove.  It worked flawlessly for the first month, heat and hot water was an endless supply.  About a month ago I was in the garage working and I heard some bubbles and running water.  I looked at tubing and could see that they were half full of air.  It didn't take long and the system air locked and quit pumping.  I have isolator valves at every exchanger so I can bypass them for maintenance or shut-off.  I put a fresh water T in the line so I can fill my system from in the house.  The pump will not overcome air in the system so I have to purge it out with fresh water, which is what I did that night.  I close off all the valves just so the pump would circulate just through the pex.  I could see tiny amounts of air flowing through the tubing which lead me to believe it was the pump.  I took the pump off and examined it for impeller damage or a leaking o-ring on the suction side, but didn't find anything obvious.  I put some silicone on the flanges and reassembled.  When I was checking things over I noticed a vibration in the pump I hadn't noticed it before; but I can't say for sure it wasn't there from the beginning.  Currently the flow is less than half of what it was originally.  I have to bleed the air out of the system every other day to keep it from shutting down completely.  The water is still 180 but the flow is so little that it's cold coming out of the heat exchanger.

I don't know what to do.  Is the pump cavitating?  What causes that and why would it suddenly do it out of the blue?  Is the seal bad in the pump?  I wouldn't think that would let air in because it is on the pressure side of the impeller.  When I started I had anti corrosive stuff in it, but due to a power outage after Christmas half the water drained down the hill and out the boilers vent tube - so that stuff is highly diluted.

I am open to any suggestions; I just need to fix this problem.

[willieG]

not sure if i can be any real help with this one ...i would begin to look at all my connections on  the lines...especially the return lines it would seem to me that if you had a small leak in a joint on the return line that it may suck air into the line and not leak..then  aside from that you could add an "air scavenger" chemical to try and keep the air out but in an open system there is usually a little gets in...also did you set your stove nice and level or slightly uphill from yhour suction line of the pump..is it possable that your water in the stove is "bubbling" and those bubbles are getting into the pump have you adjusted the temp of your stove...perhaps it is bubbling too much  and these bubbles are getting into the lines? you could maybe turn the heat of the water down a tad  and see what happens

but on another note. if it ran perfectly for a month and now acts up..what has changed in that month?
 have you added any "appliances" or changed any lines?


when i placed my stove i raised the end about 1/2 inch so any bubbles would run to the fill pipe and away from  the suction line

is your pump right on the stove..  this is a start..there may be much more help here to come...good luck and keep us posted

[willieG]

after re-reading your post the line of (the flow is half of what it was) i would try another pump first thing....if after you purge the system then the pump should pump that same as it did on day one...if not...i suspect trouble right there!

also i looked on line and i could not find any info on your pump of what its "lift" is or head pressure ect. but i suspect it is well within reason  if it worked ok for a month

[mrmopar22]

after re-reading your post the line of (the flow is half of what it was) i would try another pump first thing....if after you purge the system then the pump should pump that same as it did on day one...if not...i suspect trouble right there!

also i looked on line and i could not find any info on your pump of what its "lift" is or head pressure ect. but i suspect it is well within reason  if it worked ok for a month

half the flow is just a guess; I didn't actually measure it.  But it is significantly less than when it started.

here is a link that gives all the specs on the pump.

http://www.drillspot.com/products/70101/Bell_and_Gossett_SERIES_100_Inline_Circulator_Pump


What is there to go wrong with a pump?  How can it make air?

[markc]

i have a coalman that sits 275' from house and 25 ft below the house basement floor,  first your pump is pushing a lot of head pressure which is going to cut your flow drasticly you said you had a power out and your water drained out of the boiler even though it worked good for a while your system at the stove is non pressurized you need a water to water heat exchanger at the boiler to go from non pressurized to pressurized your pump will work at rated volum in a pressurized loop the pump paperwork will give you specs for head,  gpm, at what psi, mine requires 15.5 psi at the pump to overcome the head at 10 gpm that will take care of loosing your water in power out cases ,do you have some air scoops and auto vent in your system ? ,does your pump have a bleeder screw for bleeding the air out of it  ? and is the 12 ft of head your talking about to the highest componet in your system or your floor ,if you call me i will talk more about the componets that  i have and i can even send you a cad drawing for a pressurized system with componets
mark,502-548-9282

[mikenc]

In reading your post if it worked for a month ok something must have changed. I think  I would maybe start with pump unless you have made some changes to your piping

They do make an automatic air vent that can be installed at highest point in system which should help get rid of air and help keep it out.  Honeywell Braukmann EA 79 is one that works good from my experence.  Just put tee in line at highest point and install air vent there. Works best if you install vent out end of T looking up Not side. Should be instructions that will clarify.

You might also consider putting check valves in lines going to house. You could use swing check in supply but would probably need spring check in return. This would keep water from draing back to boiler during power outage. Not sure what pump you would need to push open spring check. Check valves should be as close to boiler as possible this should keep water in lines instead of draining back and overfilling boiler.

Just some suggestions Hope you find your problem.

[markc]

https://commcenter.insightbb.com/attach/Mark%20Cottrell%20-%20revised.jpg?sid=&mbox=INBOX&charset=escaped_unicode&uid=8810&number=6&filename=Mark%20Cottrell%20-%20revised.jpg

here is a cad drawing of a press system ,wasser pumps have check valves built in

[rosewood]

i would suspect the circ pump is sucking air threw motor shaft seal. also was your  ft/head  and gpm figured out for length / dia of pipe ,head losses of water/ air exchanges?  or something someone recomended.

[willieG]

i am not sure of how i am really reading that chart of your pump butif i am reading correctly the pump you have on yoru stove is not meant for your application the chart says it will pump 9 gallons per minute at an 8 foot head (not counting any loss due to friction on teh long horizontal run) it does not even chart anything above 8 feet of head and also says it performs  best a7 6 feet of head

i say get a pump that  is meant for what y ou really have, and that is...i am not sure becasue i dont know how to add horizontal footage and line loss due to friction
 but i would be looking for a pump gue who can map the schematic you have and give you a professional quote on what you need

i am still leaning to agree that the pump is sucking air at the shaft  due to over straining the pump

[willieG]

sorry for all the bad spelling....

[mrmopar22]

My deal is that it worked from the start; if I had problems from the beginning I would make multiple changes.  But it does seem to be getting progressively worse; now it won't keep the house warm and we have not so hot showers.  I have isolated the water flow to the house heat exchanger and it still didn't recover.  I have new pump on its way. 

My setup worked as a non-pressurized system.  The air is a new thing that emerged one night out the blue.  You can purge the majority of the air out with fresh water.  Then over the course of a couple of days the water level would drop a bit, then level off,  that’s how I knew the air was purged out.   Now it's just the opposite.  I see the water level indicator rising to a certain point - then I know the air has displaced the water.  I agree on the pumps slow death because of its deteriorating performance.

What pump would you recommend to increase volume? I don't know the progression of model numbers for B&G as a next step up.  I took a stab in the dark with the B&G 100; a business had them on their boiler that's how I got the model #.  No one could tell me what I needed; everyone around here uses the little taco or B&G 1/125 hp pumps that you can buy at Menards and it works for them; I knew from the start that wasn't going to work for me.  All the local wood burner guys just sell what the stove dealer recommends - that's why I came here for advice. 

[willieG]

after much research i am thinking that a taco pump of the size in my last post would give you a flow (your head and distance figured in and your pipe size) of about 8 to 10 gal a min  that could deliver between 100,000 and 150,000 btu an hour (you are helping me learn a lot,lol)

i am sure somewhere on here is a pump guru whom can enlighten us much more n this subject..i hope he shows soon

[markc]

go to this link it has pump comaprison graph with a head chart and gpm at each speed  do your self a favor and at least put the 11.00 honeywell auto vent in your system air lock causes steam in a pump and heat which deteriates the pump

http://heatinnovations.com/Wasser%20pump.pdf

[mrmopar22]

Here is a strange turn of events. 
Out of frustration and lack of a pump change out I isolated just the house heat exchangers by closing the valves in the garage.  I stocked the furnace and left for work.  When I got home the house was warm and the furnace fan had shut down.  I crusied into the basement to do my usual air bleed off and, to my suprise, the air had purged itself out of the system - just like it use to do.  I thought to myself, weird, and went on with my afternoon.  On my heat exchanger in the garage I had put a pepcock on the top of it to bleed air off.  With both the inlet and outlet valves closed off I opened the valve and let out a tremendous volume of pressure! (purged water and air until nothing came out) I then opened the valves and the system worked normally.  After about 4-5 hours in the garage that night I could start to hear the air bubbles in the lines again.  I went into the house and checked, sure enough, full of air and slow flow.  I was like, WTF is going on here?   So I went back to the garage and turned the valves back off - few hours go by, system back to normal.   
So you know, the garage exchanger is a brand new air-to-air intercooler of a truck chassis.  I picked the heavy duty aluminum radiator/intercooler combination for $150 - not to shabby.  New from the factory, just off last years model, so they scrapped them out - I removed the factory plugs.  It measures 13" tall, 58" long, 8" wide, with 4" inlets/outlets.  (the radiator is about 1/3 larger and was bolted to the intercooler, but that's for another building) I made plates to reduce to 1"  Pretty good deal I thought - there is a pile of them in case anyone is looking. 

My question is; why is a system that is vented to the atmosphere building pressure in the heat exchanger?  Why doesn't it do it all the time, only when I open the garage valves?  I could see if it was plugged or old or something, but it can obviously flow way more than I need.  How do I over come this?  Add a booster pump and a powered gate valve?  After all this I bought a new B&G 100 that I probably don't need - was big $$.  Now my garage is cold, so I need to find a remedy.

[rosewood]

i have a feeling your air intercooler is your problem.   why? because its design is for cooling air ,and not for exchanging water to hot air. i would think that it  is the highest component in your system ,which would explain air buildup. the cooler may be creating excess head pressure causing pump to start cavitating. i would try useing radiator instead. although i have read truck radiators do not work as well as the real thing, try for yourself. i would still try to find someone to calculate all your  ft/head  gpm requirements based on ft/dia pipe  type/model of all exchangers. don't know how they will calculate radiator? my feeling is that your current pump is going to be undersized for your application,also explaining your  pumps slow death. in another post i talked about my issues with pump sizing 101. theres really more to it than just moving water. best of luck.